1. Technical Field of the Invention
The present invention relates to a method for producing two-dimensional code which contains data desired to be concealed or kept in secret (hereinafter referred to as “secret data” or “data to be kept in secret”), and a reader for reading the two-dimensional code.
2. Background Art
Techniques for producing and reading two-dimensional codes which contain secret data are known. For example, Japanese Patent Publication (Laid-Open) No. 2004-147006 discloses an invention entitled “Information transmission method and mobile unit”. In this prior art technique, a transmission side mobile unit encrypts transmission data using encrypting keys entered through a key input device, converts the encrypted data into a QR (quick response) code serving as a two-dimensional code, and indicates the QR code on a display.
On the other hand, a reception side mobile unit reads through a camera, for example, the image of the QR code indicated on the display of the transmission side mobile unit and determines whether or not the QR code is encrypted. If yes, the encrypting keys are demanded. Then, the QR code is reverse-converted while the transmission data is decrypted using the inputted encrypting keys to indicate the decrypted data on a display.
However, according to the “Information transmission method and mobile unit” disclosed in Japanese Patent Publication (Laid-Open) No. 2004-147006, when the encrypted data have been reverse-converted into a QR code, the encrypted data per se indicated on the display such as of a mobile unit usually make no sense as character information, or on the contrary, the information may correspond to control codes that would influence the screen display control.
If the information indicated on the display makes no sense, the user of the mobile unit, for example, may have mistrust. Probably, this may inadvertently motivate a user who can recognize the information as being encrypted, to make an attempt to decrypt the information, causing a problem of security.
In addition, if the information corresponds to control codes, the screen view may be distorted, possibly leading to other system problems.